Rare gas electric discharge tube



1939- H. SCHMELLENMEIER 5 RAREGAS ELECTRIC DIS CHARGE TUBE Filed Jan. 13, 1937 Inventor I Heinz Schmellenmeier,

His Attorneg Patented Jan. 10, 19 39 UNITED STATES RARE GAS ELECTRIC DISCHARGE TUBE Heinz Schmellenmeier, Berlin-Pankow, Germany,

asslgnor to General Electric Company, a corporation of New York Application January 13, 1937, Serial No. 120,451 In, Germany January 17, 1936 12 Claims. (01. 176-424) This invention relates to rare gas electric discharge tubes which are used-for the production of light.

On account of the negative resistance characterlstic of this type of electric discharge tube it is necessary to connect a positive resistance inseries with the tube to balance the effect of the negative resistance and stabilize the operation. Under these circumstances rare gas dis: charge tubes can be operated with any current whatever, the dimensions of the tube, 1. e. the -inside diameter, the length, as well as the filling pressure of the rare gas being at random to a very great extent, and only need to be adjusted to the supply voltage. It has already been proposed, in small glow discharge tubes, to avoid the loss of energy caused by the ballast resistance, by producing an anomalous cathode drop compensating for or exceeding the negative resistance characteristic of the positive column of the discharge. This proposal has no practical meaning for electric discharge tubes with a positive column of appreciable length, because the characteristics of their electrode drops cannot be made suiilciently anomalous without great difficulty.

Objects of the present invention are to overcome the above difficulties in completely a new way, to provide a rare gas lamp of the electric discharge type having a positive resistance characteristic and capable of being operated on the usual line voltages or by the aid of a transformer without any intermediate ballast resistance or choke coil, and generally to improve the construction and operation of tubes of the kind referred to. I

I havediscovered that electric rare gas discharge tubes, even if they are of a considerable length and have electrodes of the hotoathode type, are capable of operation without a ballast resistance when a positive characteristic of the positive column discharge of such magnitude is produced that the decrease of the negative characteristics of the two electrode drops is more than compensated for. According to the present invention this is done withelectric rare gas discharge tubes having an inside diameter from 10 to 30 mm. and a rare gas pressure from 0.5 to 3 mm. mercury by adjusting the distance between the two hot electrodes so that the increase of the resistance characteristic of the positive column amounts to a higher value than that of the sum of the decrease of the characteristics of the two electrode drops. This condition can be fulfilled only in certain restricted ranges of the current between about 0.5 and 6 amperes in operation.

Current ranges of this order for neon tubes of an inside diameter of 10 mm. and 1 mm. neon pressure, for instance, are between 2 and 4 amperes. For neon tubes of 18 mm. inside diameter and 0.8 mm. neon pressure the current range is between 3 and 6 amperes; for neon tubes having a 28 mm. inside diameter and 0.6 mm. neon pressure between 4 and 5 amperes.

Before manufacturing the tubes for a given voltage and diameter this current range is established by measuring the voltage drop per cm. of the positive column of a trial tube of the same diameter, while said trial tube is still connected to the pump, for various gas pressures and currents. These values of the so-called gradient of the tube, measured by means of fine wires inserted through theglass wall of the trial tube into the discharge at certain distances, are plotted against the current in a diagram for various pressures. In nearly the same way, known to a skilled man, the characteristics of the electrode drops are measured, their values depending on the kind of electrodes used and the temperatures thereof at full operation. By combining these values according to the method cited above, the distance between the electrodes is fixed for the given voltage.

If neon is used, I have discovered that the value of the inside diameter in mm. multiplied by the filling pressure in mm. mercury must not exceed 20. If other gases than neon are used the current ranges, the inside diameter of the container and the pressure of the gas are different from the values obtained for neon, though, of course, they are in the range of values given above. If, for instance, helium is used, the current range for a tube of 18 mm. inside diameter having a gas pressure of 1 mm. is between 4 and 5 amperes, but for a tube having an inner diameter of 28 mm. and a gas pressure of 2 mm. the current range is 3.5 and 6 amperes. Using the rare gas kryuton in a tube of 20 mm. diameter and a gas pressure of 3 mm. the current range is between 0.6 and 1 ampere, but for a tube having an inner diameter of 10 mm. and a gas pressure of 0.5 mm. the current range is between 1.6 and 2.5 amperes.

In order to ensure a constant operation of the tube for a long time it has been found advisable to enlarge the vessels containing the hot electrodes so that the inside diameter thereof is at least three times as large as the inside diam-' eter of the main part of the tube. By this enlargement the vessels act as a reserve of rare gas to counteract an accelerated drop of gas pressure due to the low pressure of the filling gas. For the same purpose one or more containers may be provided at any place on the straight part of the tube, each of these containers communicating with the interior of the tube by a short pipe whose diameter must not exceed that of the tube proper. The content of each of these containers amounts to at least half the content of the tube. When desired, these containers may be provided on tubes having, in addition, enlarged vessels for the electrodes.

A preferred embodiment of this invention is shown by way of example in the drawing which illustrates a neon tube for a given direct current and voltage of 1.5 amperes and 330 volts, respectively.

The envelope or tubular vessel I of material transparent to the radiations to be transmitted, preferably glass, has two electrodes 2 and 2' of the hot cathode type sealed therein at the ends thereof. Said electrodes 2 and 2 are heated by two separate transformers 3 and 3 from a supply 4 of alternating current. The secondaries of the transformers are connected to the electrodes 2 and 2 by means of the leading-in wires 5 and 6, 5 and 6' respectively. Said envelope I has an inside diameter of mm. and is filled with neon at a pressure of 1.5 mm. mercury column. Thus the value of the inside diameter in mm. multiplied by the neon pressure in mm. equals'10 1.5=15, and thus does not exceed 20. Current is supplied to the electrodes 2 and 2| of the tube by the wires 1 and 1 which are connected across the terminals 8 of a source of direct current giving 330 volts without an intermediate resistance or choke coil. The globular electrode vessels 9 and 9' have a diameter of 35 mm. Furthermore there is a container I0 communicating with the tube l by the pipe H. The tube I may be equipped with another container l2 as illustrated in dotted lines.

The total electrode voltage drop amounts to 50 volts. By measuring the current and the voltage gradient in the manner described above, the voltage drop of the positive column had been found to be 3.3 volts per cm. tube length for the given current of 1.5 amperes, and by making the corresponding measurements for various currents i, the increase of the characteristic of the positive column was found to amount to 0.8 per cm. For the given voltage of 330 volts therefore the distance L between the electrodes is 85 cm.,- derived from L 3.3+50=330. Accordingly the characteristic of the electrode voltage drops was found to be 44. In accordance with this invention these values are to be combined with each other giving as the characteristic i. e'., the resistance characteristic of the whole tube is a positive one.

Tubes according to the invention are equipped with electrodes which may be heated by the discharge or by heating transformers. The tubes themselves may be operated with D. C., as well as with A. C. In the latter case known means are to be provided which lower the periodical restarting potential as much as possible.

I claim:

1. In combination, a discharge device having an attenuated rare gas therein, a pair of electrodes in said device, at least one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter of 10-30 mm., the pressure of said gas being so chosen within the range of .5 to 3 mm. of mercury that at a given current between .5 and 6 amperes the voltage gradient in the positive column has a positive volt-ampere characteristic, the length of said column being such that the voltage increase therein for a given increase in greater than the decrease in the sum of the electrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equal to the sum of said positive column voltage and the electrode drops at said given current, whereby said device operates stably without a series ballast.

2. In combination, a discharge device having a filling of neon therein, a pair of electrodes in said device, at least one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter of 10 to 28 mm., the pressure of said gas being so chosen within the range of 0.6 to 1 mm. of mercury that the product of the diameter of the tube in mm. multiplied by the gas pressure in mm. does not exceed 20 and that at a given current between 2 and 6 amperes the voltage gradient in the positive column has a positive volt-ampere characteristic, the length of said column being such that the voltage increase therein for a given increase in said current from the aforesaid given value is greater than the decrease in the sum of theelectrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equal to the sum of said positive column voltage and the electrode drops at said given current, whereby said device operates stably without a series ballast.

3. In combination, a discharge device having a filling of neon therein, a pair of electrodes in said device one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter of 10 mm., the pressure of said gas being 1 mm. of mercury so that at a given current between 2 and 4 amperes the voltage gradient in the positive column has a positive volt-ampere characteristic, the length of said colunm being such that the voltage increase therein for a given increase in said current from the aforesaid given value is greater than the decrease in the sum of the electrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equal to the sum of said positive column voltageand the electrode drops at said given current, whereby said device onerates stably without a series ballast.

4. In combination, a discharge device having a filling of neon therein, a pair of electrodes in said device one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter of 18 mm., the

' increase therein for a given increase in said current from the aforesaid given value is greater than the decrease in the sum of the electrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equal to the sum of said positive column voltage and the electrode drops at said given current whereby said device operates stably without a series ballast.

5. In combination, a discharge vdevice having a filling of neon therein, a pair of electrodes in said device one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter of 28 mm., the pressure of said gas being 0.6 mm. of mercury so that at a given current between 4 and 5 amperes the voltage gradient in the positive column has a positive volt-ampere characteristic,

-the length of said column being such that the voltage increase therein for a given increase in,

said current from the aforesaid given value is greater than the decrease in the sum of the electrode drops for the same increase in current and means to connect said device to'a constant potential system whose voltage is equal to the sum of said positive column voltage and the electrode drops at said given current, whereby said device operates stably without a series ballast.

6. In combination, a discharge device having a filling of helium therein, a pair oi electrodes in said device one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter 01' 18 mm., the pressure of said gas being 1 mm. of mercury so that at a given current between 4 and 5 amperes the voltage gradient in the positive column has a positive volt-ampere characteristic, the length 01' said column being such that the voltage increase therein for a given increase in said current from the aforesaid given value is greater than the decrease in the sum of the electrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equal to the sum of said positive column voltage and the electrode drops at said given current, whereby said device operatesstably without a series ballast.

7. In combination, a discharge device having a filling of helium therein, a pair of electrodes in said device one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter of 28 mm., the pressure oi said gas being 2 mm. of mercury so that at a given current between 3.5 and 6 amperes the voltage gradient in the positive column has a positive volt-ampere characteristic, the length of said column being such that the voltage increase therein for a given increase in said current from the aforesaid given value is greater than the decrease in the sum of the electrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equal to the sum oi said positive column voltage and the electrode drops at said given current, whereby said device operates stably without a series ballast. a

8. In combination, a discharge device having a filling of krypton therein, a pair of electrodes in said device one of which is 01' the thermionic t, said electrodes being separated by an arc tube having an inside diameter of mm., the pressure of said gas being 3 mm. of mercury so that at a given current between 0.6 and 1 ampere the voltage gradient in the positive column has a positive volt-ampere characteristic, the length of said column being such that the voltage increase therein for a given increase in said current from the aforesaid given value is greater than the decrease in the sum of the electrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equalto the sum of said positive column voltage and the electrode drops at said given current, whereby said device operates stably without a series ballast. t

9. In combination, a discharge device having a filling of krypton therein, a pair of electrodes in said device one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter of 10 mm., the pressure of said gas being 0.5 mm. of mercury so that at a given current between 1.6 and 2.5 amperes the voltage gradient in the positive column has a positive volt-ampere characteristic, the length of said colunm being such that the voltage increase therein for a given increase in said current from the aforesaid given value is greater than the decrease in the sum of the electrode tem whose voltage is equal to the sum of said positive column voltage and the electrode drops at said given current, whereby said device operates stably without a series ballast.

10. In combination, a discharge device having an attenuated rare gas therein, a pair of electrodes in said device, at least one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter of 10-30 mm., electrode chambers for said electrodes, said chambers having an inside diameter greater than three times the diameter of said tube, the pressure of said gas being so chosen within the range of .5-to 3 mm. of mercury that at a given current between .5 and 6 amperes the voltage gradient in the positive column has a positive volt-ampere characteristic, the length of said column being such that the voltage increase therein for a given increase in said current from the aforesaid given value is greater-than the decrease in the sum of the electrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equal to the sumor said positive column voltage and the electrode drops at said given current, whereby said device operates stably without a series ballast.

11. In combination, a discharge device having an attenuated rare gas therein, a pair oi electrodes in said device, at least one 01' which is of the thermionic type, said electrodes being separated by an arc tube having an insidediameter of 10-30 mm., off-set chambers each connected to and communicating with said tube by a short pipe having an inside diameter less than that of said tube, the volume of each of said chambers the electrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equal to the sum of said positive column voltage and the electrode drops at said given current, whereby said device operates stably without a series ballast.

12. In combination, a discharge device having an attenuated rare gas therein, a pair of electrodes in said device, at least one of which is of the thermionic type, said electrodes being separated by an arc tube having an inside diameter of 10-30 mm., electrode chambers for said electrodes, said chambers having an inside diameter greater than three times the diameter of said tube, oiT-set chambers each connected to and communicating with said tube by a short pipe having an inside diameter less than that of said tube, the volume 01' each of said chambers being at least half that of said tube, the pressure of said gas being so chosen within the range oi. .5 to 3 mm. of mercury that at a given current between .5 and 6 amperes the voltage gradient in the positive column has a positive volt-ampere characteristic, the length of said column being such that the voltage increase therein for a given increase in said current from the aforesaid given value is greater than the decrease in the sum of the electrode drops for the same increase in current and means to connect said device to a constant potential system whose voltage is equal to the sum of said positive column voltage and the electrode drops at said given current, whereby said device operates stably without a series ballast.

HEINZ SCHMELLENMEIER. 

